using System;
using static PKHeX.Core.LegalityCheckStrings;

namespace PKHeX.Core;

/// <summary>
/// Verifies the <see cref="EffortValues"/>.
/// </summary>
public sealed class EffortValueVerifier : Verifier
{
    protected override CheckIdentifier Identifier => CheckIdentifier.EVs;

    public override void Verify(LegalityAnalysis data)
    {
        var pk = data.Entity;
        if (pk is IAwakened a)
        {
            VerifyAwakenedValues(data, a);
            return;
        }
        var enc = data.EncounterMatch;
        if (pk.IsEgg)
        {
            if (pk.EVTotal is not 0)
                data.AddLine(GetInvalid(LEffortEgg));
            return;
        }

        // In Generations I and II, when a Pokémon is taken out of the Day Care, its experience will lower to the minimum value for its current level.
        int format = pk.Format;
        if (format < 3) // can abuse daycare for EV training without EXP gain
            return;

        int sum = pk.EVTotal;
        if (sum > 510) // format >= 3
            data.AddLine(GetInvalid(LEffortAbove510));
        Span<int> evs = stackalloc int[6];
        pk.GetEVs(evs);
        if (format >= 6 && evs.Find(ev => ev > 252) != default)
            data.AddLine(GetInvalid(LEffortAbove252));

        const int vitaMax = 100; // Vitamin Max
        if (format < 5) // 3/4
        {
            if (enc.LevelMin == 100) // only true for Gen4 and Format=4
            {
                // Cannot EV train at level 100 -- Certain events are distributed at level 100.
                if (evs.Find(ev => ev > vitaMax) != default) // EVs can only be increased by vitamins to a max of 100.
                    data.AddLine(GetInvalid(LEffortCap100));
            }
            else // check for gained EVs without gaining EXP -- don't check gen5+ which have wings to boost above 100.
            {
                var growth = PersonalTable.HGSS[enc.Species].EXPGrowth;
                var baseEXP = Experience.GetEXP(enc.LevelMin, growth);
                if (baseEXP == pk.EXP && evs.Find(ev => ev > vitaMax) != default)
                    data.AddLine(GetInvalid(string.Format(LEffortUntrainedCap, vitaMax)));
            }
        }

        // Only one of the following can be true: 0, 508, and x%6!=0
        if (sum == 0 && !enc.IsWithinEncounterRange(pk))
            data.AddLine(Get(LEffortEXPIncreased, Severity.Fishy));
        else if (sum == 508)
            data.AddLine(Get(LEffort2Remaining, Severity.Fishy));
        else if (evs[0] != 0 && evs.Count(evs[0]) == evs.Length)
            data.AddLine(Get(LEffortAllEqual, Severity.Fishy));
    }

    private void VerifyAwakenedValues(LegalityAnalysis data, IAwakened awakened)
    {
        var pk = data.Entity;
        int sum = pk.EVTotal;
        if (sum != 0)
            data.AddLine(GetInvalid(LEffortShouldBeZero));

        if (!awakened.AwakeningAllValid())
            data.AddLine(GetInvalid(LAwakenedCap));

        var enc = data.EncounterMatch;

        // go park transfers have 2 AVs for all stats.
        if (enc is EncounterSlot7GO)
        {
            Span<byte> avs = stackalloc byte[6];
            awakened.GetAVs(avs);
            foreach (var av in avs)
            {
                if (av >= 2)
                    continue;

                data.AddLine(GetInvalid(string.Format(LAwakenedShouldBeValue, 2)));
                break;
            }
            return;
        }

        if (awakened.AwakeningSum() == 0 && !enc.IsWithinEncounterRange(pk))
            data.AddLine(Get(LAwakenedEXPIncreased, Severity.Fishy));
    }
}